On my subway ride home last Friday evening, I shared a crowded car with a woman who was beginning to cry as we jostled through the tunnel between Manhattan and Brooklyn. They were the timid sort of tears, quiet and fragile. It was a lonely unraveling in the raucousness of rush hour.

When I saw her, my first instinct was to look away — to pretend not to notice. That’s what the rest of our neighbors were doing. In between us, a teenage boy in drooped jeans bobbed a Converse sneaker up and down against the current of the careening train, nodding sleepily to the bass beat of whatever song was pounding through his headphones. A seated, white-haired woman thumbed through her book, the kind with a fat spine and thin pages like you can buy at the airport, peeking ahead to the end of the chapter. Others numbly pressed their phone keys or simply stared at the way their hands were gripping the silver poles for balance.

The subway is a strange place where speed and stimulation are disguised as menial routine. People tend to disengage from the scene in different ways, like they’re blowing invisible bubbles around themselves for protection, pretending that they aren’t surrounded by the smells and sniffles and sharp tongues of strangers while hurtling through darkness at rapid rates they can’t control.

On a random morning this past August, I woke up to discover that I was out of almond milk. It’s a crucial component in my coffee ritual, so I ambled sleepily to the nearest grocery store for a new carton. My hair was still unbrushed, and there was nothing in my pockets but my phone and a $5 bill.

As I approached the senior center a few blocks from my apartment, I heard a soft song seeping through its shut windows: the chorus of “happy birthday.” The strangers’ voices beamed in gentle effervescence through the slits in the blinds as I stopped in my tracks. I couldn’t see their faces, but I imagined a gray-haired group of at least five people. I wondered whether there was cake. I pictured candles stuck in sloppy stacks of pancakes or waffles, with tiny flames flickering in an imitation of the waking sun.

It was a simple moment that seemed to change everything, staining my mood with its sweetness. It shook me out of my own head, which had begun buzzing with plans and to-do lists and self-focused weekday worries. It reminded me that I am not the center of the universe; that my concerns are mere specks in a world rippling with rich emotions and ever-humming human connections.

Just as the song ended with a rush of claps and scattered bursts of “yay,” I captured a quick video of the scene to sew it into my memory. My hand wobbled, and there was nothing to see, anyway. The significance was only the sound — the resonating warmth of the song whose evanescence somehow made it more poignant and precious.